A project team has begun to inject carbon dioxide into Alabama's Citronelle field as part of a $7.9 million pilot project to determine whether the field is ideal for simultaneous enhanced oil recovery and CO2 storage, the US Department of Energy said on Mar. 1.
Study results of the 7,500-ton CO2 injection will provide estimates of oil yields from EOR and storage capacity in depleted oil reservoirs, DOE's Fossil Energy Office said. Scientists from the University of Alabama at Birmingham (UAB) are leading the 5-month injection, which aims to prove whether oil remaining in domestic formations can be economically produced, it indicated.
UAB initially proposed the project involving the state's largest oil field 30 miles north-northwest of Mobile to DOE in 2006. Denbury Resources Inc., which owns and operates the field, is a partner, along with Southern Co., the Alabama Geological Survey, Alabama A&M University, and the University of North Carolina at Charlotte.
The field may be ideal for a CO2-EOR demonstration because it is composed of sandstone reservoirs in a simple structural dome and has existing infrastructure which includes deep wells, according to DOE's National Energy Technology Laboratory (NETL).
"Because of the presence of the regionally extensive Ferry Lake Anhydrite seal, four-way structural closure, and lack of faulting, it is naturally stable with respect to CO2 storage," NETL indicated in January. "However, the geology of the heterogeneous siliciclastic rocks in the field is very different from those where CO2-EOR has been applied commercially, such as in the carbonate strata of the Permian and Williston basins."
A successful demonstration could make incremental oil recovery at Citronelle field 60% greater than from the conventional secondary recovery which has occurred there, DOE's Fossil Energy Office said. It noted that Advanced Resources International of Arlington, Va., estimates that some 64 million additional bbl could be recovered with EOR at Citronelle, which was discovered in 1952.
The field's geologic structure and lack of faulting also may make it ideal for CO2 storage. NETL said that capacity of depleted oil reservoirs and saline formations in the Citronelle Dome was estimated, by static calculations, to be 500 million-2 billion short tons of CO2, "sufficient to sequester the carbon dioxide from a nearby 1,500 [Mw] coal-fired power plant for 35 years."
The project has entered its second phase, which will include injection, associated validation of models, and determination of oil-CO2 mixture properties. CO2 containment at the test site also will be monitored in the ambient air, soil and vegetation, the Fossil Energy Office said.
If the project is successful, it could encourage operates to apply CO2-EOR to other fields containing highly heterogeneous, discontinuous sands, NETL said. "Documentation of air, soil, and vegetation conditions before, during, and after the pilot tests, and the absence of environmental effects will advance the implementation and acceptance of [CO2] capture and storage by industry and the public," it added.
DOE is providing 60% of the project's financial support with an anticipated $4.7 million outlay. The remaining $3.2 million will come from the other partners.
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